The present invention relates to a method and apparatus for boring through a solid body. More particularly, the invention relates to an improved rotary drill bit for boring holes with increased efficiency through difficult to penetrate materials.
There are different drill bits for drilling through a variety of solid materials. Many of these drill bits are designed for particular applications. For instance, drill bits have been designed to drill through wood, metal, and concrete. In order to drill through these different materials, designers have varied the material used to produce the drill bits, the shape of the drill bits, and the speed with which the drill bit is operated.
One problem existing with many drill bits is the rate at which they will drill a hole is too slow. When the material to be drilled is difficult to penetrate, the process of boring a hole may take as long as several minutes. It is often important to maximize the efficiency at which a hole can be bored into a given material in order to improve manufacturing productivity. Such is the case in drilling tap holes in metal purifying blast furnaces.
The first step in producing steel sheet which is used in the building and construction industry, the automotive industry, the appliance industry, the electric motor industry, etc., is to produce relatively pure iron from iron ore. This process is carried out within a blast furnace. In order to maximize the productivity of a steelmaking facility, as much pure iron as possible must be produced. Many resources are expended in developing methods and procedures to increase the amount of pure iron which can be produced annually.
In developing these methods and procedures, every manufacturing variable in the blast furnace process is optimized. One of these variables is the rate at which the blast furnace can be tapped to drain molten iron from the furnace. A typical blast furnace is tapped from seven to twelve times per day seven days per week. The typical blast furnace tap hole takes several minutes to drill. In fact, some tap holes take as long as 15 minutes to drill.
The rate at which the tap hole is drilled is adversely affected by drill bit xe2x80x9cwalking.xe2x80x9d Walking occurs as the drill bit first meets the material to be drilled, it slides or skids laterally rather than boring into the material. Therefore, drill bit walking prevents the drill operator from initiating the drilling process.
The drilling process is also slowed by drill bit binding. Binding occurs when loosened debris created in the drilling process builds within the hole. The debris accumulates around the drill bit and freezes the drill bit within the hole preventing the drill bit from rotating within the hole.
In order to solve some of these problems, certain drill bits have been designed which have air passages. Pressurized air is forced through the passages toward the drill bit/solid body interface to blow the debris away from the drill bit and prevent binding. However, when the hole to be drilled has a substantial length, as is the case with a blast furnace tap hole, the debris continues to build because it cannot escape the hole.
The present invention is provided to solve these and other problems.
The present invention is directed to a rotary drill bit for boring a hole through solid materials. The drill bit of the present invention has interchangeable parts and increases the rate at which a hole can be drilled.
The drill bit comprises a collar and a penetrating member. The collar is attachable at a proximal end to a drill shaft and at a distal end to the penetrating member. The collar is generally centered about a longitudinal axis and has a cylindrical shape. An inner surface of the collar defines a chamber. In addition, the inner surface is furnished with reverse or lefthand oriented threads.
The penetrating member comprises a connecting end and a cutting end. The connecting end is attachable to the distal end of the collar. The connecting end has a pair of opposing planar walls joined by a pair of opposing arcuate threaded walls. The threads on the arcuate walls are reverse oriented for attachment to the reverse threads located on the inner surface of the collar. The arcuate walls have a length less than the length of the planar walls so that the cutting end has a narrow profile.
The cutting end has a pair of spades radiating from a center point. A pilot drill for creating a pilot hole is also located at the center point. Each spade has a pentagonal cross-section. Accordingly, each spade has a base wall, opposing side walls, and a pair of angled walls that intersect to form a cutting edge.